Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$166.50	3.634%	$172.5506	$172.55	$172.55	$172.60
Purchase #2	$17.90	5.359%	$18.8593	$18.86	$18.85	$18.90
Purchase #3	$75.25	13.273%	$85.2379	$85.24	$85.25	$85.20
Purchase #4	$180.39	9.277%	$197.1248	$197.12	$197.10	$197.10
Purchase #5	$28.76	12.550%	$32.3694	$32.37	$32.35	$32.40
Purchase #6	$137.89	13.219%	$156.1177	$156.12	$156.10	$156.10
Purchase #7	$171.30	6.304%	$182.0988	$182.10	$182.10	$182.10
7 purchase totals =	$777.99		$844.3585	$844.36	$844.30	$844.40